#define  _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int score=0;
	char grade;
	score >= 0 && score <= 100;
	scanf("%d", &score);
	if (score <= 100 && score >= 90)
		grade = 'A';
	if (score >= 80)
		grade = 'B';
	if (score >= 70)
		grade = 'C';
	if (score >= 60)
		grade = 'D';
	if (score < 60)
		grade = 'E';
	printf("%c", grade);









	return 0;
}